Sulfur-containing cycloaliphatic compound, filled sulfur-vulcanizable elastomer composition containing sulfur-containing cycloaliphatic compound and articles fabricated therefrom

ABSTRACT

A sulfur-containing cycloaliphatic compound, useful as a crosslinker for filled sulfur-vulcanizable elastomer compositions, is represented by the general formula: 
       G[-C a H 2a —S[C(═O)] b R] n  
 
     wherein G is selected from the group consisting of:
         saturated, monocyclic aliphatic group of valence n containing from 5 to 12 carbon atoms and optionally containing at least one halogen, and   saturated monocyclic silicone [RSiO—] n [R 2 SiO—] p  group of valence n;
 
wherein each R independently is a hydrogen or monovalent hydrocarbon of up to 20 carbon atoms; each occurrence of subscripts a and b independently is an integer wherein a is 2 to 6 and b is 0 or 1; p is an integer of from 0 to 3; and, n is an integer of from 3 to 6, with the provisos that when b is 0, R is a hydrogen atom, and when G is a non-halogenated, saturated monocyclic aliphatic group of 6 carbon atoms, n cannot be 3.

FIELD OF THE INVENTION

The present invention relates to a sulfur-containing cycloaliphaticcompound and filled sulfur-vulcanizable compositions containingorganosulfur compounds as crosslinkers (vulcanizing agents) and articlessuch as tires, tire tread, weather stripping, hose, belts, seals,gaskets, shoe soles, and the like, fabricated from such compositions.

DESCRIPTION OF THE RELATED ART

Elemental sulfur is commonly used as a vulcanizing agent for unsaturateddiene elastomers (rubbers). The crosslinks formed with sulfur areprimarily polysulfidic crosslinks that increase the thermal stability ofthe elastomer vulcanizates.

The use of organic compounds possessing sulfur-containing reactivegroups as vulcanizing agents for diene rubbers is known. Theseorganosulfur compounds often contain only two dithiocarbamate orthiosulfonate groups chemically bonded to a bridging group. The lownumber of tie points provided by such compounds results in inadequatecrosslinking of diene rubbers thus failing to achieve vulcanizatesexhibiting a satisfactory balance of wear, traction and rollingresistance. In instances where more than two dithiocarbamate orthiosulfonate groups are chemically bonded to a bridging group, thebridging group often contains unstable linkages such as ether or esterlinkages or lacks the flexibility needed to dissipate energy that canpropagate cracks when a crosslinked (cured) elastomer is subjected tomechanical stress.

It would be desirable to have a crosslinker for sulfur-vulcanizableelastomers that improves the wear properties of articles manufacturedtherefrom, e.g., weather stripping, hose, belts, seals, gaskets, shoesoles, tires and tire components, specifically, tear and abrasive wear,while maintaining hardness, lower tan delta values at temperatures above40° C. and increased tan delta values at temperatures of from 5° C. to−15° C.

SUMMARY OF THE INVENTION

One aspect of the present invention is directed to a sulfur-containingcycloaliphatic compound of the general formula (1):

G[-C_(a)H_(2a)—S[C(═O)]_(b)R]_(n)  (1)

wherein G is selected from the group consisting of:

-   -   saturated, monocyclic aliphatic group of valence n containing        from 5 to 12 carbon atoms and optionally containing at least one        halogen, and    -   saturated monocyclic silicone [RSiO—]_(n)[R₂SiO—]_(p) group of        valence n;        wherein each R independently is a hydrogen or monovalent        hydrocarbon of up to 20 carbon atoms; each occurrence of        subscripts a and b independently is an integer wherein a is 2 to        6 and b is 0 or 1; p is an integer of from 0 to 3; and, n is an        integer of from 3 to 6, with the provisos that when b is 0, R is        a hydrogen atom, and when G is a non-halogenated, saturated        monocyclic aliphatic group of 6 carbon atoms, n cannot be 3.

According to another aspect of the present invention, a curable filledelastomer composition is provided which comprises:

-   -   (i) at least one sulfur-vulcanizable elastomer;    -   (ii) at least one particulate filler; and,    -   (iii) a crosslinking effective amount of, as crosslinker for        sulfur-vulcanizable elastomer (i), at least one        sulfur-containing cycloaliphatic compound of the general        formula:

G[-C_(a)H_(2a)—S[C═O)]_(b)R]_(n)  (1)

wherein G is selected from the group consisting of:

-   -   saturated, monocyclic aliphatic group of valence n containing        from 5 to 12 carbon atoms and optionally containing at least one        halogen, and    -   saturated monocyclic silicone [RSiO—]_(n)[R₂SiO—]_(p) groups of        valence n;        wherein each R independently is a hydrogen or monovalent        hydrocarbon of up to 20 carbon atoms; each occurrence of        subscripts a and b independently is an integer wherein a is 2 to        6 and b is 0 or 1; p is an integer from 0 to 3; and, n is an        integer of from 3 to 6, with the proviso that when b is 0, R is        a hydrogen atom.

According to still another aspect of the present invention, an articlesuch as a tire or tire component such as tread, hose, belt, seal,gasket, and the like, is fabricated by molding a quantity of theforegoing curable filled elastomer composition into the shape of thedesired article and thereafter curing the composition.

In the specification and claims herein, the following terms andexpressions are to be understood as indicated.

The term “elastomer” is synonymous, and therefore interchangeable, with“rubber”.

The expression “coupling agent” means an agent capable of establishingan effective chemical and/or physical bond between a vulcanizableelastomer and its filler. Effective coupling agents have functionalgroups capable of bonding physically and/or chemically with filler, forexample, between a silicon atom of the coupling agent and the hydroxyl(OH) surface groups of the filler to form a surface-O—Si bond, e.g., asiloxane when the surface contains silanols as in the case of silica,and, for example, sulfur atoms which are capable of bonding physicallyand/or chemically with the elastomer as a result of vulcanization(curing).

The expression “filler” means a substance that is added to the elastomerto either extend the elastomer or to reinforce the elastomeric network.Reinforcing fillers are materials whose moduli are higher than theorganic polymer of the elastomeric composition and are capable ofabsorbing stress from the organic polymer when the elastomer isstrained. Fillers include fibers, particulates, and sheet-likestructures and can be composed of inorganic materials such as silicates,silica, clays, ceramics, carbon, diatomaceous earth and organicmaterials such as organic polymers. The filler can be essentially inertto the other ingredients with which it is admixed or it can be reactivetherewith.

The expression “particulate filler” means a particle or grouping ofparticles that form aggregates or agglomerates. Particulate fillers thatare useful herein can be essentially inert to coupling agents with whichthey are admixed, e.g., silane coupling agents, or they can be reactivetherewith.

The term “carrier” means a porous polymer or high surface area fillerthat has a high adsorption or absorption capability and is capable ofcarrying up to 75 percent liquid ingredient while maintaining itsfree-flowing and dry properties. Useful carriers herein are essentiallyinert to silane coupling agents and are capable of releasing ordeabsorbing liquids when added to the sulfur-vulcanizable elastomericcomposition.

Other than in the working examples or where otherwise indicated, allnumbers expressing amounts of materials, reaction conditions, timedurations, quantified properties of materials, and so forth, stated inthe specification and claims are to be understood as being modified inall instances by the term “about.”

It will be understood that any numerical range recited herein includesall sub-ranges within that range and any combination of the variousendpoints of such ranges or subranges.

It will be further understood that any compound, material or substancewhich is expressly or implicitly disclosed in the specification and/orrecited in a claim as belonging to a group of structurally,compositionally and/or functionally related compounds, materials orsubstances includes individual representatives of the group and allcombinations thereof.

DETAILED DESCRIPTION OF THE INVENTION

One aspect of the present invention is directed to a sulfur-containingcycloaliphatic compound of the general formula (1):

G[-C_(a)H_(2a)—S[C(═O)]_(b)R]_(n)  (1)

wherein G is selected from the group consisting of:

-   -   saturated, monocyclic aliphatic group of valence n containing        from 5 to 12 carbon atoms and optionally containing at least one        halogen, and    -   saturated monocyclic silicone [RSiO—]_(n)[R₂SiO—]_(p) group of        valence n;        wherein each R independently is a hydrogen or monovalent        hydrocarbon of up to 20 carbon atoms; each occurrence of        subscripts a and b independently is an integer wherein a is 2 to        6 and b is 0 or 1; p is an integer of from 0 to 3; and, n is an        integer of from 3 to 6, with the provisos that when b is 0, R is        a hydrogen atom, and when G is a non-halogenated, saturated        monocyclic aliphatic group of 6 carbon atoms, n cannot be 3.

In one specific embodiment, G is selected from a saturated monocyclicsilicone [RSiO—]_(n)[R₂SiO—]_(p) groups of valence n.

According to another aspect of the present invention, a curable filledelastomer composition is provided which comprises:

-   -   (i) at least one sulfur-vulcanizable elastomer;    -   (ii) at least one particulate filler; and,    -   (i) a crosslinking effective amount of, as crosslinker for        sulfur-vulcanizable elastomer (i), at least one        sulfur-containing cycloaliphatic compound of the general        formula:

G[-C_(a)H_(2a)—S[C═O)]_(b)R]_(n)  (1)

wherein G is selected from the group consisting of:

-   -   saturated, monocyclic aliphatic group of valence n containing        from 5 to 12 carbon atoms and optionally containing at least one        halogen, and    -   saturated monocyclic silicone [RSiO—]_(n)[R₂SiO—]_(p) groups of        valence n;        wherein each R independently is a hydrogen or monovalent        hydrocarbon of up to 20 carbon atoms; each occurrence of        subscripts a and b independently is an integer wherein a is 2 to        6 and b is 0 or 1; p is an integer from 0 to 3; and, n is an        integer of from 3 to 6, with the proviso that when b is 0, R is        a hydrogen atom.

The expression “monovalent hydrocarbon group” means any hydrocarbongroup from which one hydrogen atom has been removed and is inclusive ofalkyl, alkenyl, alkynyl, cyclic alkyl, cyclic alkenyl, cyclic alkynyl,aryl, aralkyl and arenyl.

The term “alkyl” means any monovalent, saturated straight, branched orcyclic hydrocarbon group; the term “alkenyl” means any monovalentstraight, branched, or cyclic hydrocarbon group containing one or morecarbon-carbon double bonds where the site of attachment of the group canbe either at a carbon-carbon double bond or elsewhere therein; and, theterm “alkynyl” means any monovalent straight, branched, or cyclichydrocarbon group containing one or more carbon-carbon triple bonds and,optionally, one or more carbon-carbon double bonds, where the site ofattachment of the group can be either at a carbon-carbon triple bond, acarbon-carbon double bond or elsewhere therein. Examples of alkylsinclude methyl, ethyl, propyl and isobutyl. Examples of alkenyls includevinyl, propenyl, allyl, methallyl, ethylidenyl norbornane, ethylidenenorbornyl, ethylidenyl norbornene and ethylidene norbornenyl. Examplesof alkynyls include acetylenyl, propargyl and methylacetylenyl.

The expressions “cyclic alkyl”, “cyclic alkenyl”, and “cyclic alkynyl”include bicyclic, tricyclic and higher cyclic structures as well as theaforementioned cyclic structures further substituted with alkyl,alkenyl, and/or alkynyl groups. Representative examples includenorbornyl, norbornenyl, ethylnorbornyl, ethylnorbornenyl, cyclohexyl,ethylcyclohexyl, ethylcyclohexenyl, cyclohexylcyclohexyl andcyclododecatrienyl.

The term “aryl” means any monovalent aromatic hydrocarbon group; theterm “aralkyl” means any alkyl group (as defined herein) in which one ormore hydrogen atoms have been substituted by the same number of likeand/or different aryl (as defined herein) groups; and, the term “arenyl”means any aryl group (as defined herein) in which one or more hydrogenatoms have been substituted by the same number of like and/or differentalkyl groups (as defined herein). Examples of aryls include phenyl andnaphthalenyl. Examples of aralkyls include benzyl and phenethyl.Examples of arenyls include tolyl and xylyl.

Representative non-limiting examples of saturated, monocyclic aliphaticgroups G in the sulfur-containing cycloaliphatic compounds of theinvention are trivalent, tetravalent and pentavalent cyclopentane,cyclohexane, cycloheptane, cyclooctane, cyclodecane and cyclododecane.It is to be understood that the attachment of the—C_(a)H_(2a)—S[C(═O)]_(b)R groups occurs in either an axial orequatorial stereochemical configuration about cycloalkyl ring G. Thesulfur-containing cycloaliphatic compounds herein also include mixturesof stereoisomers in which the positions of the—C_(a)H_(2a)—S[C(═O)]_(b)R groups in any one stereoisomer can all be inthe equatorial position, the axial position or both the equatorial andaxial positions. It is preferred that a mixture of stereoisomers hereincontain at least 50 weight percent of isomer in which all the—C_(a)H_(2a)—S[C(═O)]_(b)R groups are in the equatorial positionrelative to cycloaliphatic group G, and more preferably contain at least80, and most preferably at least 90, weight percent of saidstereoisomer. The stereochemistry about the cycloalkyl ring G is usuallydetermined in the preparation of the poly-alkenyl-substitutedcycloalkane intermediate or reactant. For example, in preparing1,2,4-trivinylcyclohexane from the thermal rearrangement of cis, trans,trans-1,5,9-cyclododecantriene, the reaction conditions can effect thestereochemistry about the cyclohexyl ring. Distillation of thepolyalkenyl-substituted cycloalkane or other separation methods, such aspreparative liquid chromatography can also be used to obtain the desiredratio of stereochemical isomers.

Representative and non-limiting examples of monovalent hydrocarbon groupR in the sulfur-containing cycloaliphatic compound of the invention aremethyl, ethyl, propyl, isopropyl, butyl, 2-ethylhexyl, cyclohexyl,cyclopentyl, phenyl, benzyl, tolyl, xylyl, methylbenyzl, and the like.

The divalent linking group, —C_(a)H_(2a)—, between the S[C(═O)]_(b)Rgroup and the cycloalkyl ring can be linear or branched. It is preferredthat the —C_(a)H_(2a)— group be linear with the S[C(═O)]_(b)R groupbeing on the terminal position.

Representative and non-limiting examples of the divalent linking groupare methylene, ethylene, propylene, butylene and hexylene. Preferredlinking groups are ethylene and propylene.

Representative and non-limiting examples of the sulfur-containingcycloaliphatic compounds of the invention include:2-[4,6-bis-(2-mercapto-ethyl)-2,4,6-trimethyl-[1,3,5,2,4,6]trioxatrisilinan-2-yl]-ethanethiol,thioacetic acid2-[4,6-bis-(2-acetylsulfanyl-ethyl)-2,4,6-trimethyl-[1,3,5,2,4,6]trioxatrisilinan-2-yl]-ethylester, 2-[3,4-bis-(2-mercapto-ethyl)-cyclopenyl]-ethanethiol,2-[3,5,7-tris-(2-mercapto-ethyl)-cyclooctyl]-ethanethiol,2-[3,4-bis-(2-mercapto-ethyl)-cyclohexyl]-ethanethiol,2-[3,5,7,9-tetrakis-(2-mercapto-ethyl)-cyclodecyl]-ethanethiol,2-[3,4-bis-(2-mercapto-ethyl)-cyclohexyl]-ethanethiol,3-[3,4-bis-(3-mercapto-proyl)-cyclohexyl]-propanethiol,6-[3,4-bis-(6-mercapto-hexyl)-cyclohexyl]-hexanethiol, a mixturecontaining 85 weight percent2-[cis,cis-3,4-bis-(2-mercapto-ethyl)-cyclohexyl]-ethanethiol and atleast 5 weight percent2-[trans,cis-3,4-bis-(2-mercapto-ethyl)-cyclohexyl]-ethanethiol,thioacetic acidS-{2-[3,4-bis-(2-acetylsulfanyl-ethyl)-cyclopentyl]-ethyl}ester,thioacetic acidS-{2-[3,4-bis-(2-acetylsulfanyl-ethyl)-cyclohexyl]-ethyl}ester,thioacetic acidS-{2-[3,5,7-tris-(2-acetylsulfanyl-ethyl)-cyclooctyl]-ethyl}ester,thioacetic acidS-{2-[3,5,7,9-tetrakis-(2-acetylsulfanyl-ethyl)-cyclodecyl]-ethyl}ester,thioacetic acidS-{3-[3,4-bis-(3-acetylsulfanyl-propyl)-cyclohexyl]-propyl}ester,thioacetic acidS-{6-[3,4-bis-(6-acetylsulfanyl-hexyl)-cyclohexyl]-hexyl}ester, amixture of 85 weight percent thioacetic acidS-{2-[cis,cis-3,4-bis-(2-acetylsulfanyl-ethyl)-cyclohexyl]-ethyl}esterand at least 5 weight percent thioacetic acid S-{2-[trans,cis-3,4-bis-(2-acetylsulfanyl-ethyl)-cyclohexyl]-ethyl}ester, andmixtures thereof.

Preferred sulfur-containing cycloaliphatic compounds herein include2-[3,4-bis-(2-mercapto-ethyl)-cyclohexyl]-ethanethiol, a mixturecontaining 85 weight percent2-[cis,cis-3,4-bis-(2-mercapto-ethyl)-cyclohexyl]-ethanethiol and atleast 5 weight percent2-[trans,cis-3,4-bis-(2-mercapto-ethyl)-cyclohexyl]-ethanethiol,thioacetic acidS-{2-[3,4-bis-(2-acetylsulfanyl-ethyl)-cyclohexyl]-ethyl}ester, and amixture of 85 weight percent thioacetic acidS-{2-[cis,cis-3,4-bis-(2-acetylsulfanyl-ethyl)-cyclohexyl]-ethyl}esterand at least 5 weight percent thioacetic acid S-{2-[trans,cis-3,4-bis-(2-acetylsulfanyl-ethyl)-cyclohexyl]-ethyl}ester.

The acyl-blocked mercaptan-containing cycloaliphatic compound, i.e.,when b is 1 in formula (1), is prepared by the process which comprisesreacting poly-alkenyl-substituted cycloalkane with thioacid in thepresence of a free-radical source to providepoly-thiocarboxylate-substituted alkylcycloalkane.

The mercaptan-containing cycloaliphatic compound, i.e., when b is 0 inthe formula (1), is prepared by the process which comprises:

-   -   a) reacting poly-alkenyl-substituted cycloalkane with thioacid        in the presence of a free-radical source to provide        poly-thiocarboxylate-substituted alkylcycloalkane; and    -   b) reacting poly-thiocarboxylate-substituted alkylcylcoalkane        with deblocking agent to form free poly-mercaptan-functional        alkylcycloalkane.

The foregoing process for preparing the acyl-blockedmercaptan-containing cycloaliphatic compounds of the invention isillustrated by the chemical equations for reaction steps (a)-(d):

G[-C_(c)H_(2c)CH═CH₂]_(n) +nR¹C(═O)SH→G[-C_(a)H_(2a)—SC(═O)R¹]_(n)  Step(a)

G[-C_(a)H_(2a)—SC(═O)R¹]_(n)+nHO—R²→G[-C_(a)H_(2a)—SH]_(n)+nR²OC(═O)R¹  Step (b)

wherein G is selected from the group consisting of:

-   -   saturated, monocyclic aliphatic group of valence n containing        from 5 to 12 carbon atoms and optionally containing at least one        halogen, and    -   saturated monocyclic silicone [RSiO—]_(n)[R₂SiO—]_(p) groups of        valence n;        wherein each R independently is a hydrogen or monovalent        hydrocarbon of up to 20 carbon atoms; each R¹ independently is a        monovalent hydrocarbon of up to 20 carbon atoms; each R²        independently is a monovalent hydrocarbon of up to 20 carbon        atoms; each occurrence of subscripts a and c independently is an        integer wherein a is of from 2 to 6; c is of from 0 to 4; p is        an integer of from 0 to 3; and, n is an integer of from 3 to 6.

The isomeric mixture of the sulfur-containing cycloaliphatic compoundsis determined by the stereochemistry of the polyvalent cycloaliphaticcompound containing three to six alkenyl groups,G[-C_(c)H_(2c)CH═CH₂]_(n) where G, c and n are defined above. Thestereochemical structure of the reactants is not altered in the additionreaction of the thiocarboxylic acid group in step (a).

Trivinylcyclohexanes, which are the preferred starting materials forproducing the sulfur-containing cycloaliphatic compounds of the presentinvention, can be formed by pyrolysis of 1,5,9-cyclododecatriene. Theconversion of the 1,5,9-cyclododecatriene at elevated temperature, andoptionally in the presence of a catalyst, results in the formation ofthe trivinylcyclohexane compound, as disclosed in U.S. Pat. No.3,011,003 and British Patent No. 848,637, the entire contents of whichare incorporated by reference herein.

The addition reaction of step (a) wherein the thiocarboxylic acid isreacted with a polyvalent cycloaliphatic compound containing three tofive alkenyl groups, may optionally be carried out in the presence of afree radical reagent. Suitable free radical reagents include oxidizingagents that are capable of converting the thiocarboxylic acid to athiocarboxylic acid radical, i.e., R¹C(═O)S•, and include, but are notlimited to oxygen, peroxides, hydroperoxides, and the like, and UVradiation.

In the preparation of the G[-C_(a)H_(2a)—SC(═O)R¹]_(n) intermediate,0.95 to 3 molar equivalent, preferably 1.0 to 1.25 molar equivalents andmost preferably a stoichimetric amount of thiocarboxylic acid, is used.

Effective amounts of peroxide or a hydroperoxide free radical agent canrange from 0.01 to 2, and preferably from 0.1 to 0.5, weight percent,based upon the weight of the cycloaliphatic compound containing three tosix alkenyl groups. When oxygen is used as the free radical generator,the source of the oxygen can be pure oxygen gas, air or a mixture ofoxygen and an inert gas. Mixtures of oxygen and inert gas can containfrom 3 to 15 weight percent oxygen with the balance being inert gas. Airor mixtures of oxygen and inert gas are generally preferred due to thedifficulties in handling pure oxygen in the presence of organicmaterials and of these, air is preferred. The source of UV radiation canbe a mercury lamp equipped with a quartz window.

Representative and non-limiting examples of cycloaliphatic compoundscontaining three to five alkenyl groups include1,2,4-trivinylcyclohexane, 1,2,4-tripropenylcyclohexane,1,3,5-trihexenylcyclohexane, 1,3,5,7-tetravinylcyclooctane,1,3,5,7,9-pentavinylcyclodecane, and mixtures of at least 80 weightpercent cis,cis,cis-1,2,4-trivinyl cyclohexane and at least 5 weightpercent cis-trans-cis-1,2,4-trivinylcyclohexane.

Representative and non-limiting examples of thiocarboxylic acids includethioacetic acid, thiopropanoic acid, thiobutanoic acid, thiohexanoicacid, and the like.

Representative and non-limiting examples of peroxide and hydroperoxidefree radical reagents di(2,4-dichlorobenzoyl)peroxide, tert-butylperoxypivalate, dilauroyl peroxide, dibenzoyl peroxide, tert-butylperoxy-2-ethylhexanoate,1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane,di(tert-butylperoxy)cyclohexane, tert-butylperoxy-3,5,5-trimethylhexanoate, tert-butyl peroxyacetate, tert-butylperoxybenzoate, di-tert-amyl peroxide, dicumyl peroxide,di(tert-butylperoxyisopropyl)benzene,2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl peroxyacetate,tert-butyl peroxybenzoate, di-tert-amyl peroxide, dicumyl peroxide,di(tert-butyl-peroxyisopropyl)benzene,2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl cumyl peroxide,2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, di-tert-butyl peroxide,and the like.

The addition reaction of step (a) can be carried out at sub-ambienttemperature, ambient temperature or elevated temperatures, atsub-atmospheric, atmospheric or supra-atmospheric pressure and in theabsence or presence of solvent. A suitable temperature range is from 0°C. to 200° C. and is preferably from 40° C. to 150° C. The reaction willordinarily be run to completion. The time required to achieve this willdepend upon the particular reaction conditions employed and whether acatalyst is used. Reaction time of from 5 minutes to 24 hours is usuallysuitable. Preferably, atmospheric pressure is used. Typical solventsinclude hydrocarbon solvents, including aromatic and aliphatic solvents,and chlorinated solvents.

The transesterification reaction of step (b) is effected by contactingthe G[-C_(a)H_(2a)—SC(═O)R¹]_(n) intermediate resulting from step (a)with an alcohol, optionally, in the presence of alkaline catalysts. Theamount of alcohol can vary from stoichiometric amount to a large excess.Typically, from 1 to 20 equivalents of alcohol are used to affect thetransesterification. Alternatively, the acyl group can be removed bysaponification in the present of alkali metal hydroxide. Typicalalkaline catalysts include lithium hydroxide, sodium hydroxide,potassium hydroxide, sodium methoxide, sodium ethoxide, potassiummethoxide, potassium ethoxide, and the like.

The sulfur-containing cycloaliphatic compound of the invention isparticularly useful as a crosslinker for sulfur-vulcanizable elastomers(i). The sulfur-containing cycloaliphatic compound has from 3 to 6reactive —SC(═O)_(b)R groups, which are either mercaptans or blockedmercaptans, and if blocked, the deblocking occurs during the curingreactions and generates a reactive mercaptan. The sulfur-containingcycloaliphatic compound therefore has three to five tie points to arubber molecule. Although not wishing to be constrained by theory, it isbelieved that higher numbers of tie points, such as greater than 6, canresult in a localized area in the bulk rubber that is very crowded andcannot effectively transfer stress, or energy, to the polymer chains orfillers. This transfer of stress is facilitated by the cycloaliphaticring structure. The ring controls the average distance between the—C_(a)H_(2a)—SC(═O)_(b)R groups directing them outward from the ring.The orientation enables the reactive groups to attach to differentpolymer chains thereby improving the crosslinking efficiency. Inaddition, the cycloaliphatic ring is flexible, alternating between boat,chair and twist conformations. Under high stress, the ring is able tochange to conformations that offer a pathway for absorbing energy. Inthe absence of this property, energy would be directed to bond scissionresulting in poor wear and fatigue properties in the cured rubbercomposition. Linear and branched alkyl groups are not as effective atorienting the —CH_(2a)—SC(═O)_(b)R groups. Aromatic rings are planar andstiff and therefore cannot undergo these conformational changes. Thepreferred conformation about the cycloaliphatic ring, especially whenthe ring is a 1,2,4-substituted cyclohexyl group, is the all-cisstructure. The —CH_(2a)—SC(═O)_(b)R groups at equilibrium are primarilyin the equatorial position since when the conformation changes to theall-axial positions, it is the 1,3-steric interactions that occur. Theall cis structure orients the —C_(a)H_(2a)—SC(═O)_(b)R groups away fromeach other, maximizing the average distance between the—C_(a)H_(2a)—SC(═O)_(b)R groups.

The concentration of sulfur-vulcanizable elastomer(s) (i) in the curablefilled elastomer composition herein can range from 10 to 99, preferablyfrom 50 to 95, and more preferably from 60 to 85, weight percent of theentire weight of the composition.

The concentration of particulate filler (ii) in the curable filledelastomer composition of the invention can range from 0.5 to 90,preferably from 5 to 60, and more preferably from 10 to 50, weightpercent of the entire weight of the composition.

The concentration of crosslinking sulfur-containing cycloaliphaticcompound (iii) of the invention in the filled sulfur-vulcanizableelastomer composition can range from 0.05 to 30, preferably from 0.5 to10, and more preferably from 2 to 5, weight percent of the entire weightof the composition.

Fillers can be used as carriers for liquid sulfur-containingcycloaliphatic compounds. Fillers that are used as carriers should benon-reactive with sulfur-containing cycloaliphatic compounds. Thenon-reactive nature of such fillers will be demonstrated by the abilityof a sulfur-containing cycloaliphatic compound to be extracted from thefiller at greater than 50 percent of its original loading therein usingan organic solvent. The extraction procedure is described in U.S. Pat.No. 6,005,027, the entire contents of which are incorporated byreference herein. Fillers and carriers include, but are not limited to,porous organic polymers, carbon black, diatomaceous earth, and silicas.

Reinforcing fillers useful in the present invention include fillers inwhich the silanes are reactive with the surface of the filler.Representative examples of such fillers include, but are not limited to,siliceous fillers, metal oxides such as silica (pyrogenic and/orprecipitated), titanium, aluminosilicate and alumina, clays, talc, andthe like. The fillers may be provided in the hydrated form. Particulate,precipitated silica is especially useful as filler, particularly whenthe silica has reactive surface silanols.

The porosity of a filler can be determined, e.g., by the known techniqueof mercury porosimetry. In accordance with this method, the pores of afiller are penetrated with mercury after a thermal treatment to removevolatiles. Test conditions utilize a 100 mg sample and the removal ofvolatiles over 2 hours at 105° C. and ambient to 2000 bars pressure.Mercury porosimetry may be performed according to the method describedby Winslow et al. in ASTM bulletin, p. 39 (1959) or according to DIN66133. For the measurement, a CARLO-ERBA Porosimeter 2000 may be used.The average mercury porosity specific surface area for a silica fillerherein should range from 100 to 300 m²/g.

The pore size distribution for a preferred silica, alumina oraluminosilicate filler according to such mercury porosity measurement isconsidered herein to be such that five percent or less of its pores havea diameter of less than 10 nm, 60 to 90 percent of its pores have adiameter of 10 to 100 nm, 10 to 30 percent of its pores have a diameterat 100 to 1,000 nm and 5 to 20 percent of its pores have a diameter ofgreater than 1,000 nm.

Suitable silica fillers include those having an average particle size,e.g., in the range of from 10 to 50 nm as determined by electronmicroscopy, although smaller and larger particle sizes are also useful.Various commercially available silicas that are suitable for use hereininclude, e.g., those from PPG Industries such as HI-SIL 210 and HI-SIL243, etc.; those from Rhone-Poulenc such as ZEOSIL 1165 MP; those fromDegussa such as VN2 and VN3, etc., and those from Huber such as HUBERSIL8745.

In one embodiment, one or more fillers are combined with silane couplingagent. The filler can be a mixture of siliceous filler such as silica,alumina and/or aluminosilicate and a carbon black reinforcing pigment.Thus, the filler component can be a mixture of from 15 to 95 weightpercent of siliceous filler with the balance being carbon black, e.g.,one having a CTAB value of from 80 to 150, and can contain from 0.1 to20 weight percent of a silane coupling agent, including, illustratively,one or more of 3-mercaptopropyltriethoxysilane,bis-(3-triethoxysilylpropyl)tetrasulfide,bis-(3-triethoxysilylpropyl)disulfide, S-thiooctanonic acid,3-triethoxysilylpropyl ester, and a silylated core polysulfide, thestructure of which are described in U.S. published patent applications2008/0161461 and 2008/0161477, the entire contents of which areincorporated by reference herein. In another embodiment, the weightratio of siliceous filler to carbon black is at least 3 to 1, preferablyat least 10 to 1 and more preferably at least 30 to 1.

Filler mixtures can contain from 60 to 95 weight percent of silica,alumina and/or aluminosilicate and, correspondingly, from 40 to 5 weightpercent carbon black, and from 0.1 to 20 weight percent silane couplingagent, with the proviso that the mixture of the components add up to 100percent. The siliceous filler and carbon black may be pre-blended orblended together in the manufacture of the vulcanized rubber.

Sulfur-vulcanizable elastomers (i) herein include conjugated dienehomopolymers and copolymers and copolymers of at least one conjugateddiene and aromatic vinyl compound. Suitable organic polymers forpreparation of rubber compositions are well known in the art and aredescribed in various textbooks including “The Vanderbilt RubberHandbook,” Ohm, R. F., R. T. Vanderbilt Company, Inc., 1990 and in the“Manual for the Rubber Industry,” Kemperman, T. and Koch, S. Jr., BayerA G, LeverKusen, 1993.

In one embodiment of the present invention, the sulfur-vulcanizableelastomer is solution-prepared styrene-butadiene rubber (SSBR), e.g.,one having a styrene content of from 5 to 50, and preferably from 9 to36, percent. In other embodiments of the present invention, thesulfur-vulcanizable elastomer is selected from the group consisting ofemulsion-prepared styrene-butadiene rubber (ESBR), natural rubber (NR),ethylene-propylene copolymers and terpolymers (EP, EPDM),acrylonitrile-butadiene rubber (NBR), polybutadiene (BR), and the like,and mixtures thereof.

Suitable conjugated diene elastomers include, but are not limited to,isoprene and 1,3-butadiene and suitable vinyl aromatic elastomersinclude, but are not limited to, styrene and alpha methyl styrene.Useful polybutadienes include those typically containing about 90percent by weight of the units in the cis-1,4-butadiene form.

The sulfur-vulcanizable elastomer (i) may be selected, e.g., from atleast one of cis-1,4-polyisoprene rubber (natural and/or synthetic),emulsion polymerization-prepared styrene/butadiene copolymer rubber,organic solution polymerization-prepared styrene/butadiene rubber,3,4-polyisoprene rubber, isoprene/butadiene rubber,styrene/isoprene/butadiene terpolymer rubber, cis-1,4-polybutadiene,medium vinyl polybutadiene rubber (35-50 percent vinyl), high vinylpolybutadiene rubber (50-75 percent vinyl), styrene/isoprene copolymers,emulsion polymerization-prepared styrene/butadiene/acrylonitrileterpolymer rubber and butadiene/acrylonitrile copolymer rubber. For someapplications, an emulsion polymerization-prepared styrene/butadiene(ESBR) having a relatively conventional styrene content of from 20 to 28percent bound styrene, or an ESBR having a medium to relatively highbound styrene content of from 30 to 45 percent, may be used.

Emulsion polymerization-prepared styrene/butadiene/acrylonitrileterpolymer rubbers containing from 2 to 40 weight percent boundacrylonitrile in the terpolymer are also contemplated as diene basedrubbers for use in this invention.

The cured, i.e., vulcanized, elastomer composition herein contains asufficient amount of filler(s) (ii) as to exhibit a reasonably highmodulus, as for example a modulus at 100 percent strain of greater than8 MPa, and high resistance to tear, as for example, a tear strength ofgreater than 25 N. In one embodiment of the present invention, thecombined weight of the filler may be as low as 5 to 100 parts perhundred parts (phr). In another embodiment, the combined weight of thefiller is from 25 to 85 phr and at least one precipitated silica isutilized as a filler in another embodiment. The silica may becharacterized as having a BET surface area, as measured using nitrogengas, from 40 to 600, and preferably from 50 to 300, m²/g. The BET methodof measuring surface area is described in the Journal of the AmericanChemical Society, Volume 60, page 304 (1930). The silica may also becharacterized as having a dibutylphthalate (DBP) absorption value offrom 100 to 350, and preferably of from 150 to 300. Further, the silica,as well as the aforesaid alumina and aluminosilicate, may have a CTABsurface area of from 100 to 220. CTAB surface area is the externalsurface area as determined with cetyl trimethylammonium bromide with apH of about 9. The method is described in ASTM D 3849.

In practice, a vulcanized elastomer article is typically prepared bythermomechanically mixing the sulfur-vulcanizable elastomer(s) (i),filler(s) (ii) and sulfur-containing cycloaliphatic crosslinker(s) (iii)in a sequentially step-wise manner to provide a curable elastomerfollowed by molding and curing the compositions to provide the article.First, for the aforesaid mixing of the sulfur-vulcanizable elastomer(s)and other components, typically exclusive of the sulfur-containingcycloaliphatic crosslinker, sulfur and sulfur vulcanization accelerators(collectively, curing agents), the elastomer (s) and various elastomercompounding ingredients typically are blended in at least one, and often(in the case of silica-filled low rolling resistance tires) two or more,preparatory thermomechanical mixing stage(s) in suitable mixers. Suchpreparatory mixing is referred to as nonproductive mixing ornon-productive mixing steps or stages. Such preparatory mixing usuallyis conducted at temperatures of from 140° C. to 200° C., and for somecompositions from 150° C. to 170° C. Subsequent to such preparatory mixstages, in a final mixing stage, sometimes referred to as a productivemixing stage, curing agents, and possibly one or more additionalingredients, are mixed with the rubber compound or composition at lowertemperatures, e.g., from 50° C. to 130° C., in order to prevent orretard premature curing of the sulfur-vulcanizable rubber, sometimesreferred to as scorching. The rubber mixture, also referred to as arubber compound or composition, typically is allowed to cool, sometimesafter or during a process of intermediate mill mixing, between theaforesaid various mixing steps, for example, to a temperature of about50° C. or lower. When it is desired to mold and cure a filled curableelastomer composition, the desired quantity of the composition isintroduced into a mold of appropriate configuration and at a temperatureof from 130° C. to 200° C., vulcanization of the rubber is achievedthrough reaction with the sulfur-containing groups of thesulfur-containing cycloaliphatic crosslinker herein and any othersources of free sulfur that may be present in the composition.

Thermomechanical mixing refers to the phenomenon whereby under the highshear conditions in a rubber mixer, the shear forces and associatedfriction occurring as a result of mixing the rubber compound, or someblend of the rubber compound itself and rubber compounding ingredientsin the high shear mixer, the temperature autogeneously increases, i.e.,it “heats up”. Several chemical reactions may occur at various steps inthe mixing and curing processes.

One or more other sulfur sources may be used, for example, in the formof elemental sulfur such as, but not limited to, S₈. A sulfur donor isconsidered herein to be a sulfur-containing compound which liberatesfree, or elemental, sulfur at a temperature in the range of from 140° C.to 190° C. Such sulfur donors include polysulfide vulcanizationaccelerators and organosilane polysulfides with at least two connectingsulfur atoms in their polysulfide bridges. The amount of free sulfursource in the curable composition herein can be controlled or adjustedas a matter of choice relatively independently of the addition of thesulfur-containing cycloaliphatic crosslinker.

In one embodiment of the invention, the rubber composition can comprise100 parts by weight rubber (phr) of at least one sulfur-vulcanizablerubber selected from the group consisting of conjugated dienehomopolymers and copolymers, and copolymers of at least one conjugateddiene and aromatic vinyl compound, from 5 to 100 phr, and preferablyfrom 25 to 80 phr, of at least one filler, up to 5 phr curing agent, andfrom 0.05 to 25 phr of at least one sulfur-containing cycloaliphaticcompound of the present invention as crosslinker.

In another embodiment, the filler composition can comprise from 1 to 85weight percent carbon black based on the total weight of the fillercomposition and from 0.5 to 10 parts by weight of at least onesulfur-containing cycloaliphatic compound of the present invention ascrosslinker based on the total weight of the rubber composition.

The rubber composition can be prepared by first blending rubber, fillerand silane coupling agent, or rubber and filler pretreated with all or aportion of the silane coupling agent, if needed, in a firstthermomechanical mixing step to a temperature of from 120° C. to 200° C.for from 2 to 20 minutes. The sulfur-containing cycloaliphaticcrosslinker and other curing agent(s), if present, are then added in asubsequent thermomechanical mixing step at a temperature of from 50° C.to 100° C. for 1 to 30 minutes. The temperature is then increased tofrom 130° C. to 200° C. with curing being accomplished in from 5 to 60minutes.

In another embodiment of the present invention, the process may alsocomprise the additional steps of preparing an assembly of a tire orsulfur-vulcanizable rubber with a tread comprised of the rubbercomposition prepared according to this invention and vulcanizing theassembly at a temperature in the range of from 130° C. to 200° C.

Other optional ingredients may be added in the rubber compositions ofthe present invention including coupling agents, e.g., silane couplingagents, curing aids, e.g., sulfur compounds, including activators,retarders and accelerators, processing additives such as oils,plasticizers, tackifying resins, silicas, other fillers, pigments, fattyacids, zinc oxide, waxes, antioxidants and antiozonants, peptizingagents, reinforcing materials such as, for example, carbon black, and soforth. Such additives are selected based upon the intended use and onthe sulfur vulcanizable material selected for use, and such selection iswithin the knowledge of one of skill in the art, as are the requiredamounts of such additives known to one of skill in the art.

The vulcanization may be conducted in the presence of additional sulfurvulcanizing agents. Examples of suitable sulfur vulcanizing agentsinclude, for example elemental sulfur (free sulfur) or sulfur-donatingvulcanizing agents, for example, an amino disulfide, polymericpolysulfide or sulfur olefin adducts which are conventionally added inthe final, productive, rubber composition mixing step. The sulfurvulcanizing agents, which are common in the art are used, or added inthe productive mixing stage, in an amount ranging from 0.4 to 3 phr, oreven in some circumstances up to 8 phr, with a range of from 1.5 to 2.5phr in one embodiment and from 2 to 2.5 phr in another embodiment.

Vulcanization accelerators, i.e., additional sulfur donors, may be usedherein, e.g., benzothiazoles, alkyl thiuram disulfides, guanidinederivatives and thiocarbamates. Specific representatives of theseaccelerators include mercapto benzothiazole, tetramethyl thiuramdisulfide, benzothiazole disulfide, diphenylguanidine, zincdithiocarbamate, alkylphenoldisulfide, zinc butyl xanthate,N-dicyclohexyl-2-benzothiazolesulfenamide,N-cyclohexyl-2-benzothiazolesulfenamide,N-oxydiethylenebenzothiazole-2-sulfenamide, N,N-diphenylthiourea,dithiocarbamylsulfenamide, N,N-diisopropylbenzothiozole-2-sulfenamide,zinc-2-mercaptotoluimidazole, dithiobis(N-methyl piperazine),dithiobis(N-beta-hydroxy ethyl piperazine) and dithiobis(dibenzylamine). Other sulfur donors include, e.g., thiuram and morpholinederivatives. Specific representatives of such donors includedimorpholine disulfide, dimorpholine tetrasulfide, tetramethyl thiuramtetrasulfide, benzothiazyl-2,N-dithiomorpholide, thioplasts,dipentamethylenethiuram hexasulfide and disulfidecaprolactam.

Accelerators are used to control the time and/or temperature requiredfor vulcanization and to improve the properties of the vulcanizate. Inone embodiment, a single accelerator system may be used, i.e., a primaryaccelerator. Conventionally, a primary accelerator is used in totalamounts ranging from 0.5 to 4, and preferably from 0.8 to 1.5, phr.Combinations of primary and a secondary accelerators can also be usedwith the secondary accelerator being present in smaller amounts, e.g.,from 0.05 to about 3 phr, in order to activate and to improve theproperties of the vulcanizate. Delayed action accelerators and/orvulcanization retarders may also be used. Suitable types of acceleratorsare amines, disulfides, guanidines, thioureas, thiazoles, thiurams,sulfenamides, dithiocarbamates and xanthates. In one embodiment, theprimary accelerator is a sulfenamide. If a second accelerator is used,the secondary accelerator can be a guanidine, dithiocarbamate or thiuramcompound.

Typical amounts of tackifier resins, if used, are from 0.5 to 10 phr,and preferably from 1 to 5 phr. Typical amounts of processing aids are 1to 50 phr. Suitable processing aids include, e.g., aromatic, naphthenicand/or paraffinic processing oils. Typical amounts of antioxidants arefrom 1 to 5 phr. Representative antioxidants includediphenyl-p-phenylenediamine and others, such as, for example, thoseidentified in the “Vanderbilt Rubber Handbook” (1978), pages 344-346.Typical amounts of antiozonants are from 1 to 5 phr. Typical amounts offatty acids, e.g., stearic acid, if used are from 0.5 to 3 phr. Typicalamounts of zinc oxide are from 2 to 5 phr. Typical amounts of waxes,e.g., microcrystalline waxes, are from 1 to 5 phr. Typical amounts ofpeptizers, e.g., pentachlorothiophenol and dibenzamidodiphenyldisulfide, are from 0.1 to 1 phr.

The cured rubber compositions of this invention can be used for variouspurposes such as the manufacture of tires, weather stripping, hose,belts, seals, gaskets, shoe soles, and the like. In one embodiment ofthe present invention, the rubber compositions described herein areparticularly useful for manufacturing tire treads but can be used forall other parts of a tire as well. The tires can be built, shaped,molded and cured by any of various methods which are well known to thoseskilled in the art.

The examples presented illustrate the synthesis of sulfur-containingcycloaliphatic compounds herein and their use as crosslinkers for filledsulfur-vulcanizable elastomer compositions.

Example 1

This example illustrates the preparation of thioacetic acidS-{2-[3,4-bis-(2-acetylsulfanyl-ethyl)-cyclohexyl]-ethyl}ester whosestructure is:

Thioacetic acid (1,974 grams, 25.9 mol.) was charged into a 5-literround bottom flask. Air was bubbled into the thioacetic acid using aflitted tube. 1,2,4-Trivinylcyclohexane (1,303 grams, 8.0 mol.) wasadded dropwise using an addition funnel over a period of 2.5 hours. Anexotherm was observed. The temperature was maintained at 32° C. using anice bath. After 4 hours, the ice bath was removed and the reactionmixture was stirred for an additional 16 hours while air was beingbubbled through the reaction mixture. The excess thioacetic acid wasremoved by stripping the solution under vacuum at approximately 100° C.The yield was quantitative, producing 3,137 grams of product. GCanalysis confirmed that the reaction was complete.

Example 2

This example illustrates the preparation of2-[3,4-bis-(2-mercapto-ethyl)-cyclohexyl]-ethanethiol whose structureis:

The acyl group was removed by the transesterification reaction. Thethioacetic acidS-{2-[3,4-bis-(2-acetylsulfanyl-ethyl)-cyclohexyl]-ethyl}ester (3,090grams, 7.9 mol.), that was prepared in Example 1, was charged to a5-liter round bottom flask. Ethanol (1,070 grams, 23.3 mol.) and sodiumethoxide (68.6 grams) was added with stirring. The mixture was heated torefluxing conditions for 4 hours and the ethyl acetate that formed wasremoved by distillation at atmospheric pressure. An additional amount ofethanol (672 grams, 15.6 mol.) was added and the mixture was refluxedovernight. The ethanol and ethyl acetate were removed by distillation.The addition of ethanol and removal of ethanol and ethyl acetate wasrepeated two more times. The2-[3,4-bis-(2-mercapto-ethyl)-cyclohexyl]-ethanethiol (1,884 grams) wasa pale yellow hazy liquid.

Example 3

This example illustrates the preparation of an isomeric mixturecontaining 84.82 weight percent thioacetic acidS-{2-[3,4-bis-(2-acetylsulfanyl-ethyl)-cyclohexyl]-ethyl}ester.

A mixture of stereochemical isomers of 1,2,4-trivinylcyclohexane wasprepared by fractional distillation. The distillation unit consisted ofa 5-liter round bottom flask, a strip silvered column (inner diameter of51 mm, height of 1,470 mm) equipped with stainless steel flat meshscreen supporting a 316 stainless steel Propac 0.16 mesh ball, sizerating 0.16 inch packing material, and a reflux condenser.Trivinylcyclohexane (4,150 grams) and 4-tert-butylcatechol (4.5 grams)were charged to the flask. The pressure was reduced to within the rangeof 6.5 torr to 7.3 ton and the temperature to within the range of 90.0°C. to 90.8° C. The boiling rate was maintain at 6 drops per second. Thedistillated was collected and analyzed by gas chromatography. The gaschromatography column and conditions were a DB-5 column, 30 meters long,0.32 millimeter internal diameter, 0.25 micron film, a flame ionizationdetector, 60 psi air, 50 psi helium and 30 psi hydrogen pressure. Thetemperature profile had a starting temperature of 80° C., a ramp at 10°C. per minute to 25° C., a hold for 10 minutes at 250° C., a second rampat 10° C. per minute to 300° C. and a final hold of 5 minutes at 300° C.the mixture was composed of a low boiling isomer (84.2 weight percent),a slightly higher boiling isomer (14.4 weight percent) and a mixture oftwo high boiling isomers (1.3 weight percent). The low boiling componentwas assigned to the cis,cis,cis-1,2,4-trivinylcyclohexane. The otherthree isomers contain both cis and trans stereochemistry.

The 1,2,4-trivinylcyclohexane containing 84.2 weight percentcis,cis-1,2,4-trivinylcyclohexane isomer, was used to prepare anisomeric mixture containing 84.2 weight percent thioacetic acidS-{2-[cis,cis-3,4-bis-(2-acetylsulfanyl-ethyl)-cyclohexyl]-ethyl}esteraccording to the procedures of Example 1.

Example 4

This example illustrates the preparation of a mixture containing 84.2weight percent of the isomer2-[cis,cis-3,4-bis-(2-mercapto-ethyl)-cyclohexyl]-ethanethiol.

The isomeric mixture containing 84.2 weight percent thioacetic acidS-{2-[cis,cis-3,4-bis-(2-acetylsulfanyl-ethyl)-cyclohexyl]-ethyl}esterthat was prepared in Example 3 was used as a starting material. Thetransesterification reaction was accomplished using the procedure ofExample 2.

Comparative Example 1

This comparative example illustrates the preparation of3-mercapto-propionic acid 2,2-bis-(3-mercapto-propionyloxymethyl)-butylester whose structure is:

This compound was purchased from Aldrich Chemical Company, product38,148-9.

Comparative Example 2

This comparative example illustrates the preparation of3-Mercapto-propionic acid3-(3-mercapto-propionyloxy)-2,2-bis-(3-mercapto-propionyloxymethyl)-propylester whose structure is:

This compound was purchased from Aldrich Chemical Company, product44,178-3.

Comparative Example 3 and Example 5 Measurements and Testing of theRubber Compositions

The measurement made and the tests used to characterize the rubbercompositions are described below. The rubber compositions werecharacterized before and after curing as indicated below.

The rheological properties of the compositions were measured on aMonsanto R-100 Oscillating Disk Rheometer and a Monsanto M1400 MooneyViscometer. The specimens for measuring the mechanical properties werecut from 6 mm plaques cured for (t90+1) minutes at 149° C. Curing andtesting of the cured rubber compositions in the form of plaques werecarried out according to ASTM standards. In addition, small straindynamic tests were carried out on a Rheometrics Dynamic Analyzer(ARES—Rheometrics Inc.). Payne effect strain sweeps were carried outfrom dynamic strain amplitudes of 0.01% to about 25% shear strainamplitude at 10 Hz and 60° C. The dynamic parameters, G′_(initial), ΔG′,G″_(max) and tan δ_(max), were extracted from the non-linear responsesof the rubber compounds at small strains. In some cases, steady statevalues of tan δ were measured after 15 minutes of dynamic oscillationsat strain amplitudes of 35% (at 60° C.). Temperature dependence ofdynamic properties was also measured from about −80° C. to +80° C. atsmall strain amplitudes (1 or 2%) at a frequency of 10 Hz.

The specific curing procedure and measurement procedures were asfollows:

Mooney viscosity and scorch ASTM D1646 Oscillating disc rheometry ASTMD2084 Curing of test plaques ASTM D3182 Stress-strain properties ASTMD412 Heat build-up ASTM D623

The formulations of the rubber compositions are set forth in Table 1 andthe test results are presented in Table 2.

TABLE 1 Summer Passenger Car Tread Compounding Formulations Comp. Ex. 3Ex. 5 Masterbatch phr Phr Styrene-butadiene rubber 77 77 cis Butylrubber 23 23 Silica 95 95 Carbon black 3.0 3.0 Aromatic oil 35.0 35.0Stearic Acid 2.5 2.5 Zinc Oxide 2.5 2.5 6PPD 2.0 2.0 TMQ 2.0 2.0 Wax 2.02.0 Silane 8.075 8.075 Masterbatch 252.1 252.1 Sulfur 2.0 2.0 CBS 2.02.0 DPG 2.0 2.0 Compound from Ex. 2 0.625

The commercial sources of the components of the tread formulations ofTable 1 are as follows: styrene-butadiene rubber: Buna VSL 5025 (non-oilextended) from Lanxess; silica: Zeosil 1165 MP from Rhodia; carbon black(N-330); process oil: Sundex 8125 from Sun Oil; ZnO: Kadox 720C fromZincCorp.; stearic acid: Industrene R from Witco, Crompton; 6 PPD:(Flexzone 7P from Uniroyal); TMQ: Naugard Q from Crompton; wax: SunproofImproved from Uniroyal, Crompton; sulfur: Rubbermakers

Sulfur 104 from Harwick; CBS: Delac S from Uniroyal, Crompton; DPG: DPGfrom Uniroyal, Crompton; silane: Silquest A-1589 silane from MomentivePerformance Materials.

TABLE 2 Summer Passenger Car Tread Compounding Results RubberComposition, Comp. Property Units Ex. 3 Ex. 5 Cure, t95 Min. 14.57 16.88M_(H)-M_(L) 27.82 25.88  50% Modulus MPa 1.3 1.2 100% Modulus MPa 2.42.4 300% Modulus MPa 15.2 15.9 Tensile MPa 17.1 14.8 Elongation % 332280 Hardness RT Shore A 61.0 57.3 Rebound RT % 38.6 38.7 Rebound 70° C.% 60.1 60.0 Delta rebound 21.5 21.3 Tear Strength N 34.6 31.3

These results indicate that2-[3,4-bis-(2-mercapto-ethyl)-cyclohexyl]-ethanethiol was equivalent inrebound and modulus to the control that does not have thesulfur-containing cycloaliphatic compounds.

Comparative Examples 5-7 and Example 6

Rubber compositions were prepared wherein the formulations were basedupon natural rubber (NR). These formulations are representative forrubber compositions used in truck tire tread. The mixing, curing andtesting procedures were identical to Example 5. The formulations are setforth in Table 3 and the test results are presented in Table 4.

TABLE 3 Truck NR Tread Compounding Formulations Comp. Comp. Comp. Ex. 5Ex. 6 Ex. 6 Ex. 7 Masterbatch phr phr phr Phr Natural Rubber 100 100 100100 Carbon black 48.5 48.5 48.5 48.5 Mineral oil 2.4 2.4 2.4 2.4 StearicAcid 2.0 2.0 2.0 2.0 Zinc Oxide 3.0 3.0 3.0 3.0 6PPD 1.5 1.5 1.5 1.5DTPD 1.0 1.0 1.0 1.0 Wax 2.5 2.5 2.5 2.5 Masterbatch 160.9 160.9 160.9160.9 Sulfur 1.4 1.4 1.4 1.4 TBBS 1.6 1.6 1.6 1.6 CTP 0.1 0.1 0.1 0.1Additive from Ex. 1 0.62 Additive from Comp. Ex. 1 0.92 Additive fromComp. Ex. 2 0.85

The commercial sources of the tread formulations of Table 3 are definedas follows: natural rubber: (SMR-L); TBBS: Delac NS from Uniroyal; CTP:carbon treated phthalic anhydride retarder from Lanxess; carbon black(N-330); zinc oxide: Kadox 720C from ZincCorp.; stearic acid: IndustreneR from Witco, Crompton; 6PPD: Flexzone 7P from Uniroyal; wax: SunproofImproved from Uniroyal, Crompton; sulfur: Rubbermakers Sulfur 104 fromHarwick.

TABLE 4 Truck Natural Rubber Tread Compounding Results RubberComposition, Comp. Comp. Comp. Property Units Ex. 5 Ex. 6 Ex 6 Ex. 7Cure, t95 Min. 11.4 8.46 14.22 8.05 M_(H)-M_(L) 35.48 34.93 39.31 35.6150% Modulus MPa 1.3 1.4 1.7 1.3 100% Modulus MPa 2.66 2.73 3.10 2.62300% Modulus MPa 14.63 14.20 14.42 14.10 Tensile MPa 31.13 28.92 29.7631.15 Elongation % 524 517 528 527 Hardness RT Shore A 63.0 64.4 69.562.2 Rebound RT % 52.9 49.1 43.3 47.8 Rebound 70° C. % 63.1 60.4 54.655.6 Delta rebound 13.1 13.6 11.1 12.8 Tear Strength N 280.4 294.7 262.5295.7

Although the rubber compositions referred to in the examples above havebeen described as truck tread compositions, these rubber compositionsare expected to be suitable for other industrial rubber-based goods,including, illustratively, for conveyor belts.

Examples 7 and 8

A model shoe sole formulation as described in Table 5 below and a mixprocedure are used to evaluate representative examples of thethiocarbamoyldisulfanyl-functional cycloaliphatic compounds of thepresent invention. The mixing is done as follows in a “B” BANBURY®(Farrell Corp.) mixer with a 103-cubic inch (1,690-cubic centimeter)chamber volume. The mixing of the rubber is done in two steps. The firststep is to prepare a Masterbatch. The mixer is turned on with the mixerat speed number 2 and full cooling water. The rubber polymers are addedto the mixer and is ram down mixed for 30 seconds. Half of the silica isadded to the mixer and is ram down mixed for 30 seconds. Half of thesilica and the oil are added to the mixer and are ram down mixed for 30seconds. All of the remaining ingredients of the rubber compound areadded to the mixer and are ram down mixed for 30 seconds. The mixer isdusted down and the mixture is ram down mixed for 15 seconds, and thenthe speed is increased to number 3 and is ram down mixed for anadditional 15 seconds. The rubber is dumped (removed from the mixer), asheet is formed on a roll mill set at about 49° C. to 55° C., and thenis allowed to cool to ambient temperature.

In the second step, the final mixture is prepared. The rubber compoundprepared in the first step is recharged into the roll mill at about 49°C. to 55° C. and the curative package is added. The curative package ismixed in and then is cut six times on each side. A sheet is formed on aroll mill set and then is allowed to cool to ambient temperature.

TABLE 5 Model Shoe Sole Compounding Formulation Ex. 7 Ex. 8 Ingredientsphr Phr Natural rubber 20 20 Nitrile rubber 20 20 Cis-Butyl rubber 60 60Silica 42 42 Diethylene glycol 2 2 BHT 1 1 Zinc Oxide 4 4 Stearic acid 11 Activator 1.5 1.5 Disperser 2.0 2.0 Homogenizer 2 2 Wax 1.0 1.0 Silane1.5 1.5 Sulfur 2 2 MBTS 1.0 1.0 MBT 0.2 0.2 TMTM 0.15 0.15 Crosslinkerfrom Example 1 2.5 Crosslinker from Example 2 2.5

The commercial sources of the components of the shoe sole formulationsof Table 5 are as follows: cis-butadiene rubber: Budene 1207 fromGoodyear Corporation; natural rubber: (SMR-L); nitrile rubber: PerbunanNT 2445 form Bayer; silica: HiSil 233 form PPG; diethylene glycol fromDow Corporation; BHT: butylated hydroxytoluene from Asia Pacific; ZnO:Kadox 720C from ZincCorp.; stearic acid: Industrene R from Witco,Crompton; wax: Sunolite 240 from Witco Corporation; activator: Rhenofit2555 from Rhein-Chemie; dispenser: Aflux 12 from Rhein-Chemie;homogenizer: Phenosin N260 from Rhein-Chemie; sulfur: Rhenogran S-80from Rhein-Chemie; MBTS: Thiofide from Flexsys; MBT: Thiotax MBT fromFlexsys; TM™: Rhenogran TM™ form Rhein-Chemie; silane: Silquest A-1289silane from Momentive Performance Materials.

Comparative Examples 8-10 and Examples 9-12

The rubber compositions of Table 6 were mixed in an instrumented “OOC”BANBURY® mixer with a 2,600 cubic centimeter chamber volume. The mixingof the rubber was done in three steps. The mixer was turned on with themixer at 80 rpm and the cooling water at 71° C. The rubber polymers wereadded to the mixer and ram down mixed for 30 seconds. The fillers andthe silane were added to the mixer and ram down mixed for 30 seconds.The other ingredients of the rubber compound of Table 1 except for theoils were added to the mixer and ram down mixed for 60 seconds. Themixer speed was reduced to 65 rpm and then the oils were added to themixer and ram down mixed for 60 seconds. The mixer throat was dusteddown and the ingredients ram down mixed until the temperature reached150° C. The ingredients were then mixed for an additional 3 minutes and30 seconds. The mixer speed was adjusted to hold the temperature between150° C. and 155° C. The rubber was dumped (removed from the mixer), asheet was formed on a roll mill set at about 85° C. to 90° C., and thenallowed to cool to ambient temperature.

In the second step, the rubber compound of the first step was rechargedinto the mixer. The mixer's speed was 80 rpm, the cooling water was setat 71° C. and the ram pressure was set at 25 psi. The mixture was ramdown mixed for 150 seconds while the temperature was brought up to 150°C., and then the mixer was reduced to 50 rpm. The rubber was mixed for40 seconds at temperatures between 150° C. and 155° C. After mixing, therubber was dumped (removed from the mixer) and a sheet was formed on aroll mill set at about 85° C. to 90° C. The rubber was allowed to coolto ambient temperature.

In a third step, the mixer speed was set to 50 rpm, the cooling waterwas set at 71° C. and the ram pressure was set at 25 psi. The rubbercompound of the second step and the curatives were ram down mixed for190 seconds while the temperature of the final mixture was brought up to115° C. After mixing, the rubber was dumped (removed from the mixer), asheet was formed on a roll mill set at about 85° C. to 90° C., and thenallowed to cool to ambient temperature. The curing condition was 160° C.for 20 minutes.

The performance of the sulfur-containing cycloaliphatic compounds of thepresent invention is demonstrated in a truck tread composition. Therubber formulations are set forth in Table 6 and the test results arepresented in Table 7. The test procedures were described in thefollowing ASTM and DIN methods:

Mooney Scorch ASTM D1646 Mooney Viscosity ASTM D1646 Rheometer (MDR2000) DIN 53 529 Storage Modulus, Loss Modulus, Tensile and ElongationDIN 53 504-R1 Shore A Hardness DIN 53 505 Rebound DIN 53 512, ASTM D1054DIN Abrasion DIN 53 516

TABLE 6 Truck Tread Compounding Formulation Comp. Comp. Ex. 8 Ex. 9 Ex.10 Ex. 9 Ex. 11 Comp. Ex. 10 Ex. 12 Ingredients Phr phr Phr phr phr phrphr Natural rubber 100 100 100 100 100 100 100 Carbon Black 48 48 48 4848 48 48 Process aid 2.4 2.4 2.4 2.4 2.4 2.4 2.4 Anti-aging 6 6 6 6 6 66 Stearic Acid 2 2 2 2 2 2 2 Zinc Oxide 3 3 3 3 3 3 3 Sulfur 1.6 1.251.25 1.2 1.08 0.55 0.46 TBBS 0.8 0.88 0.8 1.2 1.2 2.6 2.6 Crosslinker —1.016 1.484 — 1.016 — 1.016 from Ex. 1

The commercial sources of the components of the tread formulations ofTable 1 are as follows: natural rubber: (SMR-L); carbon black (N-220);ZnO: Kadox 720C from ZincCorp.; stearic acid: Industrene R from Witco,Crompton; TBBS: Delac NS from Uniroyal, Crompton; sulfur: RubbermakersSulfur 104 from Harwick.

TABLE 7 Truck Tread Rubber Composition Test Results Rubber Comp. Ex.Comp. Ex. Comp. Ex. Composition, Property Units Ex. 8 Ex. 9 10 Ex. 9 11Ex. 10 12 Specific Gravity g/cm³ 1.090 1.098 1.098 1.097 1.097 1.0951.095 MDR 2000 at 160° C. Time (Cure state) - Min. 2.6 2.85 2.86 2.973.01 3.25 3.29 10 Time (Cure state) - Min. 6.36 6.48 6.43 6.09 6.18 8.048.50 90 ML dNm 2.77 2.64 2.61 2.68 2.54 2.47 2.40 MHF dNm 15.98 14.3314.00 16.05 15.08 15.31 13.70 MHF − ML dNm 13.21 11.69 11.39 13.37 12.5412.84 11.30  50% Modulus MPa 1.163 1.0070.995 1.14 1.048 1.058 0.948100% Modulus MPa 2.067 1.709 1.688 2.028 1.814 1.908 1.620 300% ModulusMPa 12.6 10.8 10.7 12.9 11.6 12.8 11.0 Tensile RT MPa 25.4 23.7 23.625.1 24.6 24.5 22.2 Elongation % 537 556 555 527 549 517 521 Shore A RTShore A 60.2 58.1 57.3 60.6 58.9 59.5 58.5 Shore A 70° C. Shore A 55.752.3 51.4 54.8 53.1 54.3 51.5 Resilience RT % 46.3 43.1 43.6 46.8 44.446.8 42.3 Rebound 70° C. % 59.1 56.7 58.2 60.4 58.3 59.0 55.2 HSTE MJ/m³7.69 10.64 10.95 7.53 9.71 6.79 10.74 LTA RT Monsanto (life timeanalysis) Applied strain Percent 30 30 30 30 30 30 30 Cycle (median) KC105.5 151.2 147.2 131.6 153.9 96.1 129.9 Graves 100° C. tear N/mm 61.5566.48 73.90 72.32 76.30 54.02 57.75 resistance

The cured truck tread compound had a significant improvement in Gravestear resistance. For example, Example 10 has a 20 percent improvement inGraves tear resistance, when compared to the control formulation withoutthe crosslinker from Example 1 (Comparative Example 8). Similarly, LTART Monsanto life time analysis improved from 105.5 for ComparativeExample 8 to 147.2 for Example 10, a 40 percent improvement.

Although the rubber compositions referred to in the examples above havebeen described as truck tread compositions, these rubber compositionsare expected to be suitable for other industrial rubber-based goods,including, illustratively, for conveyor belts.

Other embodiments of the invention will be apparent to those skilled inthe art from a consideration of this specification or practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with the true scope and spiritof the invention being defined by the following claims.

1.-15. (canceled)
 16. A filled sulfur-vulcanizable elastomer compositionwhich comprises: (i) at least one sulfur-vulcanizable elastomer; (ii) atleast one particulate filler; and, (iii) a crosslinking effective amountof, as crosslinker for sulfur-vulcanizable elastomer (i), at least onesulfur-containing compound of the general formula (1):G[-C_(a)H_(2a)—S[C(═O)]_(b)R]_(n)  (1) wherein: G is selected from thegroup consisting of a saturated, monocyclic aliphatic group of valence ncontaining from 5 to 12 carbon atoms, optionally containing at least onehalogen, and a saturated monocyclic silicone group of valence n; each Ris a hydrogen; each occurrence of subscripts a and b is independently aninteger wherein a is 2 to 6; b is 0; and, n is an integer of from 3 to6.
 17. The filled sulfur-vulcanizable elastomer composition of claim 16wherein sulfur-vulcanizable elastomer (i) is at least one memberselected from the group consisting of ethylene-propylene copolymer (EP),ethylene-propylene-diene terpolymer (EPDM), cis-1,4-polyisoprene rubber,emulsion polymerization-prepared styrene/butadiene copolymer rubber,organic solution polymerization-prepared styrene/butadiene rubber,3,4-polyisoprene rubber, isoprene/butadiene rubber,styrene/isoprene/butadiene terpolymer rubber, cis-1,4-polybutadienerubber, medium vinyl polybutadiene rubber, high vinyl polybutadienerubber, styrene/isoprene copolymer, emulsion polymerization-preparedstyrene/butadiene/acrylonitrile terpolymer rubber,butadiene/acrylonitrile copolymer rubber, emulsionpolymerization-derived styrene/butadiene (ESBR) having a styrene contentof from 20 to 28 percent bound styrene, and an ESBR having a medium torelatively high bound styrene content of from 30 to 45 percent.
 18. Thefilled sulfur-vulcanizable elastomer composition of claim 17, whereinthe amount of sulfur-vulcanizable elastomer (i) is from 10 to 99 weightpercent of the entire weight of the composition.
 19. The filledsulfur-vulcanizable elastomer composition of claim 18, wherein theamount of sulfur-vulcanizable elastomer (i) is from 60 to 85 weightpercent of the entire weight of the composition.
 20. The filledsulfur-vulcanizable elastomer composition of claim 16 whereinparticulate filler (ii) is at least one member selected from the groupconsisting of inert porous filler for carrying silane and filler that isreactive for silane, the filler being combined with at least one silanepossessing functionality that is reactive for sulfur-vulcanizableelastomer (i).
 21. The filled sulfur-vulcanizable elastomer compositionof claim 20 wherein particulate filler (ii) is from 0.5 to 90 weightpercent of the entire weight of the composition.
 22. The filledsulfur-vulcanizable elastomer composition of claim 21 whereinparticulate filler (ii) is from 10 to 50, weight percent of the entireweight of the composition.
 23. The filled sulfur-vulcanizable elastomercomposition of claim 20 wherein the inert porous filler is carbon andthe filler that is reactive for silane is silica.
 24. The filledsulfur-vulcanizable elastomer of claim 20 wherein the silane is asilylated core polysulfide.
 25. The filled sulfur-vulcanizable elastomerof claim 24 wherein the filler that is reactive for silane is silica.26. The filled sulfur-vulcanizable elastomer composition of claim 16wherein G in sulfur-containing cycloaliphatic compound (iii) is derivedfrom a cyclopentane, cyclohexane or cycloheptane group.
 27. The filledsulfur-vulcanizable elastomer composition of claim 16 whereinsulfur-containing cycloaliphatic compound (iii) is at least 50 weightpercent of the mixture has an isomer in which the—C_(a)H_(2a)—S(C═O)_(b)R groups are in the equatorial position relativeto group G.
 28. The filled sulfur-vulcanizable elastomer composition ofclaim 16 wherein sulfur-containing cycloaliphatic compound (iii) is atleast one member of the group consisting of2-[4,6-bis-(2-mercapto-ethyl)-2,4,6-trimethyl-[1,3,5,2,4,6]trioxatrisilinan-2-yl]ethanethiol;2-[3,4-bis-(2-mercapto-ethyl)-cyclopenyl]-ethanethiol;2-[3,5,7-tris-(2-mercapto-ethyl)-cyclooctyl]-ethanethiol;2-[3,4-bis-(2-mercapto-ethyl)-cyclohexyl]-ethanethiol;2-[3,5,7,9-tetrakis-(2-mercapto-ethyl)-cyclodecyl]-ethanethiol;2-[3,4-bis-(2-mercapto-ethyl)-cyclohexyl]-ethanethiol;3-[3,4-bis-(3-mercapto-propyl)-cyclohexyl]-propanethiol;6-[3,4-bis-(6-mercapto-hexyl)-cyclohexyl]-hexanethiol; and a. mixturecontaining 85 weight percent2-[cis,cis-3,4-bis-(2-mercapto-ethyl)-cyclohexyl]-ethanethiol and atleast 5 weight percent2-[trans,cis-3,4-bis-(2-mercapto-ethyl)-cyclohexyl]-ethanethiol.
 29. Thefilled sulfur-vulcanizable elastomer composition of claim 28, whereinsulfur-containing cycloaliphatic compound (iii) is2-[3,4-bis-(2-mercapto-ethyl)-cyclohexyl]-ethanethiol.
 30. The filledsulfur-vulcanizable elastomer composition of claim 29, wherein thesulfur-containing cycloaliphatic compound (iii) is a. mixture containing85 weight percent2-[cis,cis-3,4-bis-(2-mercapto-ethyl)-cyclohexyl]-ethanethiol and atleast 5 weight percent2-[trans,cis-3,4-bis-(2-mercapto-ethyl)-cyclohexyl]-ethanethiol.
 31. Thefilled sulfur-vulcanizable elastomer composition of claim 16, wherein Gin sulfur-containing compound (iii) is derived from a saturatedmonocyclic silicone group of valence n.
 32. The filledsulfur-vulcanizable elastomer composition of claim 16, whereinsulfur-containing compound (iii) is2-[4,6-bis-(2-mercapto-ethyl)-2,4,6-trimethyl-[1,3,5,2,4,6]trioxatrisilinan-2-yl]-ethanethiol.33. The cured composition of claim
 16. 34. The cured composition ofclaim
 28. 35. The cured composition of claim 33 provided as a weatherstripping, hose, belt, seal, gasket or shoe sole.
 36. The curedcomposition of claim 34 provided as a weather stripping, hose, belt,seal, gasket or shoe sole.